A Belgian Method of Preserving Hops

MEETING HELD THURSDAY, 24th MARCH, 1898, AT THE GRAND HOTEL, BIRMINGHAM.

Mr. J. E. Bowly (Vice-President), in the Chair.

The following paper was read and discussed :—

A Belgian Method of Preserving Hops
By Norbert Van Laer

The preservation of hops is a question which occupies the attention of nearly every brewer at the present time. I need not speak to you on the subject of cold storage as this system is already well known. The short paper I have the pleasure of reading before you tonight, is upon a special method of treating hops which I had the opportunity of seeing in Belgium last summer.

Having found this method practical and useful, to a certain extent, to brewers in that country, I thought it might be interesting to give you a few words as to its working.

As you know, hops continually undergo change when in contact with the air, some of the various useful principles being oxidised; consequently, they lose their commercial value, and moreover, acquire after a certain time an unpleasant odour and taste which makes them unfit for brewing purposes. The useful substances are attacked and modified by the action of the air and the moisture—thus, the tannic acid undergoes by hydrolysis a transformation into gallic acid, which has no beneficial effect upon beer wort. The resins, on their part, become more and more insoluble, and lastly the essential oil under goes a change, which communicates an objectionable odour and taste to the beer. The useful substances found in the leaves, such as tannic acid and the resins, are not so quickly attacked as those in the lupulin, therefore they can be preserved better.

The lupulin holds the aroma, the resin, and the greater part of the bitter substance. The bracts which compose the cone, contain a little resin, tannin, and bitter substance which is distributed in the cellulose, which constitutes the framework of the bracts. In other words the lupulin contains the active principles in a very small volume, while in the leaves these principles are distributed over a mass of inert matter, viz., the cellulose which enters into about 70 per cent, of the composition of the hop cone.

In the process used in Belgium, great care is taken not to touch the lupulin or the oil it contains, the bracts being simply detached by special screens, but in order to separate the lupulin from the bracts the hops are slightly dried at a temperature not exceeding 90° F., so that they will not lose their aroma. Afterwards the hops are put into a revolving screen fitted with brushes which detach the lupulin from the bracts, and cause it to fall through the meshes of the metallic web, and the bracts are carried to the end of the machine and discharged into baskets. The leaves are then free from lupulin and are afterwards put into a series of “diffusers,” similar to those used on the Continent in the manufacture of sugar from beetroot.

Tepid water continually circulates within these “diffusers” (12 in number), passing from the first to the second and so on, coming out of the last charged with the hop extract. The circulation of the water continues until a drop of water evaporated on a slip of glass leaves no trace of extract. The operation is then finished.

The extract thus obtained is afterwards run into a vacuum pan where it is evaporated until the liquid becomes a thick syrup. The lupulin which was collected alone is then intimately mixed with this syrup, then the whole is pot into hermetically sealed boxes from which the air has been exhausted and replaced by carbonic acid gas.

This process involves no deterioration of any of the useful principles of the hop, and thus prepared it is named in Belgium “Normal Hop.” This hop extract docs not vary, it preserves its aromatic qualities and virtues for an indefinite period.

The use of this hop extract which I shall henceforth call “Normal Hop,” offers the following advantages to brewers :—

(1) It does away with the large stores that are necessary for hops in bulk, which large warehouses have to be specially arranged with regard to ventilation, temperature, and dryness. By using “Normal Hop” a brewer can, in a small space, store sufficient for his requirements for a year or more.

(2) The preservation of the products for an indefinite period :— The certainty of preservation allows the brewer to provide for several years when hops are at a low price, which is appreciable, because in a bad year, hops often attain several times their ordinary value, such as in the years 1882 and 1883.

(3) Regularity in hopping:— With this “Normal Hop,” the brewer can produce a beer which will have the same aroma. At all times his beers will contain the same fixed and volatile principles.

(4) A notable economy results in the employment of such hops:— The “Normal Hop” immediately yields its useful principles to the wort, while the exhaustion of the natural hop is never complete in the copper, even after several hours’ boiling, a period which is injurious, because bitter principles are extracted from the stalks which pass into the beer and make it disagreeable.

In the treatment of the hops about which I have spoken to you, care is taken to remove all the stalks from the hops before submitting them to the action of the diffuser.

We have just seen by this process, that beyond doubt all the active principles of the hops have been preserved intact successfully. First, because the principles upon which the method of working is based are in conformity with the admitted facts of science, and secondly, because practical experience of many years has confirmed it.

Method of using the “Normal Hop.”—Formerly brewers contented themselves by adding the hop extract to the copper half an hour before turning off. Under these conditions all the extractive matters were dissolved and retained in the wort, but a certain amount of the aroma volatilized, and it is preferable to use the hops in the following manner:—Take 2 or 3 gallons of boiling wort from the copper and mix the “Normal Hop” with it in a closed vessel, let the vessel remain in the boiling wort in the copper for a quarter of an hour, then empty the contents into the copper five minutes before turning out. This method is to be preferred to the other, because there is less loss of aroma, and all the hop extract is equally dissolved and mixed with the wort.

I do not pretend that it is necessary to do away entirely with the use of natural hops and use “Normal Hop,” as if is necessary to have cellulose or some other inert matter in the copper in order to obtain a proper boiling of the substances contained in the wort. Further, this cellulose acts as a filter for the wort, in the hopback. What in contended is that at least a third of the quantity of hops used in a brewery can be easily replaced by this “Normal Hop” to the great advantage of the quality of the product and an economy which may be estimated at from 30 to 40 per cent.

DISCUSSION

The CHAIRMAN asked how the filtration in the hop back was preserved in the absence of hops when the extract was used.

Mr. F. L. TALBOT inquired the cost of transforming natural hops into hop extract.

Mr. R. CLARKE asked if the contents of the tin boxes would deteriorate if opened some time before using.

Mr. W. W. BUTLER inquired whether in extracting hops with water in the diffusers, it was not possible that matters would be extracted which did not pass into solution when hops were boiled in the copper with wort. Then again, although the liquid appeared to have been evaporated at a low temperature, there seemed to be an indication of charring. He could not understand the production of such a dark extract from hops, and would like to know whether any oxidation or charring took place. Were the germs of the hops destroyed in the process? If not, it seemed to him that even that pasty mass would ferment, or be subject to some sort of decomposition.

Mr. VAN LAER said that the hop extract did not replace more than one-third of the natural hops, so that there would be enough of the latter for purposes of filtration in the hop back. The cost of making extract in Belgium would be the price of the hops plus the carriage, which was 1s, 6d. per cwt. from London. The total cost for manipulation, tin boxes, cases, and carriage would be about 15s. per cwt. In the process of treating the hops the bracts were separated from the stalks, which contained bitter substances, which would communicate a very unpleasant taste to the beer. The tannic acid was extracted from the bracts, together with the remainder of the resins which had survived the brushing and screening process. This was a very different matter to extracting the whole of the hops, including stalks and cone. With regard to the colour of the extract, that was due to the concentration of the liquid coming from the diffusers, which was evaporated in a vacuum. No oxidation or charring took place, the extract being in such a concentrated form, and the boxes charged with carbonic acid, that no change occurred. Moreover, if there were any decomposition, the hops could not be kept for several years. He had seen some which had been kept in boxes for 12 years, and were then as fresh as on the first day they were placed in the boxes.

Mr. BUTLER remarked that there seemed to be a peculiar odour given off when the box was opened.

Mr. VAN LAER said that the hop extract he exhibited was from Bavarian hops, and the peculiar odour was due to the hops themselves In such a concentrated form, it was impossible to detect the natural odour so well as when the hop extract was diluted with hot water.

Mr. G. T. HARRAP, speaking from an engineering point of view, said it seemed to him that a large amount of plant would be required to carry out the process, and if it cost 15s. per cwt. to carry it out, the cold storage system was the most advantageous. Under Briant and Meacham’s system they could store hops for mouths and no deterioration or discoloration took place.

Mr. VAN LAER said with regard to deterioration they did not open the boxes until they required to use the extract. When he mentioned 15s. per cwt., that was the cost of carrying out the process in Belgium, but if the extract were prepared in England it would come to about the present price of cold storage. After hops had been converted into extract the latter could be kept for any length of time.

Mr. J. G. WELLS said it seemed to him, from the sample of extract which he had seen, that the delicate flavour of the hops was lost. He was disappointed when he smelt the extract, and thought that the absence of the ordinary aroma was a weak point. It was well known that in the concentration and evaporation of organic substances there was a deterioration of flavour, and he was afraid that in the process described this had taken place, and, if so, that would militate against the successful use of the extract. He would like to know whether the process had ever been applied to English hop?, and he would have liked to have seen some beers brewed with the extract compared with some brewed with ordinary hops.

Mr. VAN LAER said he had no experience with regard to English beer brewed with this hop extract, but he had tested a number of samples of Belgian top-fermentation beers brewed with as much as 40 per cent, of hop extract, and not the slightest abnormality could be detected in flavour or quality as compared with the same beers brewed with ordinary hops.

Mr. BUTLER asked whether it was contended that the resins were not altered in the evaporation or concentration.

Mr. VAN LAER said that the resins were extracted by brushing through a kind of screen, and were caught in a basket. The bracts were pulled from the stalks, and only the bracts went into the diffusers.

Mr. BUTLER asked if the author considered that it was a concentrated solution of tannic acid which was obtained.

Mr. VAN LAER said practically speaking it was a syrup, consisting almost entirely of tannic acid.

Mr. CLARKE asked whether, by using 30 per cent, of the extract, the author considered that new hops, or yearling hops, could be replaced.

Mr. VAN LAER replied in the affirmative. Many years’ experience in Belgium had proved it to be so.